Aircraft Propeller CFD Simulation Using Mesh Motion, ANSYS Fluent Training

Description

A propulsion is a device that converts mechanical force into thrust in aircraft and ships. The movement of air or water provides the necessary thrust. A propeller consists of two or more twisted blades. When the propeller rotates around its axis, the lift produced by these blades moves the air in a horizontal direction.

In advanced systems, the propellers are responsible for converting the rotational power of the engine crankshaft (piston engines) into propulsion. This force is equal to the product of the mass of air pushed back by the propeller per second and the velocity given to the airflow.

If a person is standing on the ground behind a rotating propeller while the aircraft is stationary, he can fully feel the airflow. In principle, the propeller blade is like a small wing that produces aerodynamic force.

This aerodynamic force can be broken down into one component of the force along the axis of the aircraft (propulsion force) and another component in the propeller blade plate (torque force).

In this project, the analysis of thrust and lift forces behind the propeller on the fuselage is examined by ANSYS Fluent software.

First, the geometry of the plane and the propeller in Solidworks software are designed and modeled to create the mesh, create the grid, and name the boundary conditions.

The geometry file is implemented in ANSYS Meshing software. The mesh is carried out in ANSYS Meshing software. The elements are first used as tetrahedral and then polyhedral mesh Fluent, which has fewer cells and better quality.

The element number equals 3812519 for tetrahedral and 692023 for polyhedral mesh type.

Aircraft Methodology

Aircraft and propeller modeling is performed in two zones, rotational and stationary. Using the Mesh Motion method, the computational domain must rotate around the impeller axis to model the impeller rotational motion.

Due to the greater importance of the impeller in the problem results, it is preferable to mesh around it with more refined elements. The cylindrical computational domain around the impeller with a value of 1.12 impeller diameter is considered, and in that area, the meshing is done more accurately.

The rotational domain is located inside the fixed zone and is separated using an interface that transfers values ​​​​between these two domains. Also, the solver is Transient.

Scaling analysis for rotational impeller simulation is such that the number of advanced coefficients must be paid for in this modeling. According to the table below, the advanced coefficient is based on the relationships used for similar samples.

Tip Speed Ratio (TSR) = 1/ J = V/(n*d)

D: impeller diameter = 0.0532 m

n: impeller speed = 1800 rpm = 30 rad/s

As a result, for J = 1.225, the flow velocity is calculated at 2 m/s.

According to the calculations performed, these boundary conditions can be used to simulate different propeller scales.

Aircraft Conclusion

The results obtained from the simulation of lift and drag values for the fuselage are also the thrust and torque values for the propeller, which are shown in the following diagrams.

In the present work, simulations have been performed around the plane and the propeller, and the values ​​​​of drag and lift force on the fuselage and thrust and torque on the impeller have been obtained.

Also, the contours, vectors, and flow lines represent the flow physics formed around this. This modeling showed that by observing the advance ratio for each propeller, working points could be defined as the relationship between flow velocity and propeller rotational speed.

But more specifically, we need more criteria to have an entirely correct simulation, such as the Reynolds number based on the impeller speed and flow velocity.

From experimental studies and previous work, it can be seen that to simulate rotating impellers, and it is necessary to use the Advance Ratio criterion with the propeller speed and velocity values in terms of the criteria of the two Reynolds numbers mentioned above.

For a similar propeller, it is valid that the Reynolds calculated with these numbers be larger than the critical Reynolds for that particular propeller. In this case, it can model and simulate aircraft and propellers based on the advanced ratio of real work points.